The present invention relates to a photographic printing method and an apparatus therefor.
In large scale photofinishing laboratories developed photographic films, having a plurality of picture frames formed thereon, are inspected to determine correction values for each picture frame. Such photographic films are formed with a notch for indicating a reference position, and the correction values of each picture frame are effected by the use of a notch puncher before making prints therefrom. When printing, a film is measured to detect characteristic values of each picture frame before placing the picture frame of the film in a printing or exposure position. Then, the picture frame of the film is placed in the printing position so as to be exposed with an exposure level according to the exposure correction values and to the characteristic values. Such a photographic printer is provided with a notch sensor disposed before a picture frame is placed in a printing position to detect each notch formed in the film. The transportation or movement of the film is controlled based on a distance between the notches which indicates the reference position, and which is detected by counting driving pulses applied to a pulse motor. A specific picture frame and the correction value of the specific picture frame are determined by the counted number of notches.
In recent years, various photographic printing systems (i.e., so called mini-labo (mini-laboratory) systems) have become widespread. These systems are simplified systematically in their operation in order to make prints with ease.
Such systematized mini-labo photographic printers are so structured as to place picture frames in a printing position for effecting an image inspection and for printing frame by frame. In such a frame inspection, the film is inspected visually to determine whether each picture frame of a negative film is placed in a proper position and whether a picture frame will possibly fail or not be printed during the printing process. According to the result of this inspection, a position correction is induced if a picture frame is placed with a deviation from the printing position, and exposure correction data is entered in the photographic printer through correction keys for a picture frame which is evaluated to possibly produce a failure in its print. After this inspection, when a print key is operated, the picture frame is measured to detect a density or light transmittance so as to calculate exposures for three colors based on the measured density or light transmittance and on the previously entered exposure correction data. Thereafter, printing control is effected according to the calculated exposures to make a print of the picture frame.
In such printing systems, since each picture frame is placed in the printing position only once for effective inspection and printing alternately, the photographic printer restricts the operator for a long time, resulting in a high printing cost.
In an attempt at solving such problems in association with those photographic printers, there is disclosed in, for example, Japanese Patent Unexamined Publication No. 61-91,648 a printing method in which a film is first transported in one direction to inspect picture frames thereof one by one and, thereafter, in the opposite direction to print each picture frame. In each of the inspection and print processes, the picture frames of the film are positioned in a correct printing position. For the positioning of film, a notch sensor is used to detect notches which are provided previously on the film. More particularly, one notch is provided for each picture frame in order to automatically position the picture frame in the printing position.
A problem associated with such a photographic printing method is that when a positioning notch of an associated picture frame deviates from the center line thereof, it is difficult for the picture frame to be automatically placed in a correct position. In addition, such a photographic printing method is hardly applicable to mini-labo systems in which no notches are formed in films.
In order to avoid these problems in association with the conventional printing methods, there has been disclosed in Japanese Patent Application No. 61-244,357, filed by the same applicant as this application, a method in which a film is transported by a pulse motor and is placed in the print position by counting driving pulse applied to the pulses motor. In this method, each picture frame of the film is, after a manual position correction, if needed, positionally specified by storing the number of the counted driving pulses as position data in a memory. In a print process, the position data is read out from the memory, and by using the position data, the picture frame is automatically placed in the printing position.
In this method, of a pulse motor is used to move the film, and the use of the number of driving pulses applied to the pulse motor as position data problems occur is used. More specifically, since a position error increases cumulatively if the pulse motor pulls out, it becomes hard to place each picture frame in position once the pulse motor pulls out. Furthermore, in the case of using the number of driving pulses applied to the pulse motor as position data, a great number of driving pulses are counted and, therefore, a large capacity of memory is necessary to memorize position data.
It is therefore an object of the present invention to provide a photographic printing method and an apparatus therefor in which no cumulative position error occurs, and in which only a small capacity of memory is needed to store memory position data for a large number of picture frames.